c‐erbB‐2 and c‐erbA‐1 (ear‐1) Gene Amplification and c‐erbB‐2 Protein Expression in Japanese Breast Cancers: Their Relationship to the Histology and Other Disease Parameters

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Abstract
We studied c‐erbB‐2 and c‐erbA‐1 (ear‐1) gene amplification, and c‐erbB‐2 protein expression in 123 primary Japanese breast cancers. c‐erbB‐2 amplification was found in 19 of the 123 tumors (15%), and c‐erbA‐1 was coamplified in 7 of the 19. The presence or absence of c‐erbB‐2 amplification correlated with the grade of cellular atypism (P= 0.008), or that of mitotic index (P= 0.002), but not with the histologic types. The tumor size (P= 0.04) and the lymph node status (P= 0.06) were associated, but the patients’ age, the TNM stage, or the presence or absence of estrogen or progesterone receptors was not associated, with c‐erbB‐2 amplification. There were no differences in the histologic type, cellular atypism, mitotic index, and other disease parameters between tumors with c‐erbB‐2 amplification only and those with coamplification of c‐erbB‐2 and c‐erbA‐1. Paraffin sections from all 19 tumors with c‐erbB‐2 amplification, and those from only one of 104 tumors without the amplification were positively stained with polyclonal anti‐c‐erbB‐2 protein antibody. Since the correlation between the amplification and the protein expression was excellent, such immunohistochemical studies may be substituted for the time‐consuming DNA studies using Southern blotting.